The introduction of high-performance networking between servers and storage assets has caused storage technology to undergo a rapid transformation. The viability of new storage technologies has been affirmed by the rapid adoption of networked storage by virtually every large enterprise and institution. Since the early 1990s, storage innovation has produced a steady stream of new technology solutions, including Fibre Channel, network-attached storage (NAS), server clustering, serverless backup, high-availability dual-pathing, point-in-time data copy, shared tape access, Internet small computer system interface (iSCSI), common information model (CIM)-based management of storage assets and transports, and storage virtualization.
Storage virtualization is the logical abstraction of physical storage systems and may be enabled to hide the complexity of physical storage devices and their specific requirements from management view. Storage virtualization may have tremendous potential for simplifying storage administration and reducing costs for managing diverse storage assets.
The redundant arrays of inexpensive disks (RAID) technology was intended to enhance storage performance and provide data recoverability against disk failure. It also streamlined storage management by reducing disk administration from many physical objects to a single virtual one. Storage virtualization technologies leverage lower-level virtualizing techniques such as RAID, but primarily focus on virtualizing higher-level storage systems and storage processes instead of discrete disk components.
The introduction of storage networking has centralized storage administrative tasks by consolidating dispersed direct-attached storage assets into larger, shared resources on a storage area network (SAN). Fewer administrators may be able to manage more disk capacity and support more servers, but capacity for each server may still be monitored, logical units manually created and assigned, zones established and exported, and new storage assets manually brought online to service new application requirements. In addition, although shared storage may represent a major technological advance over direct-attached storage, it has introduced its own complexity in terms of implementation and support. Finding ways to hide complexity, automate tedious tasks, streamline administration, and still satisfy the requirements of high performance and data availability are challenging tasks.
Another highly advertised objective for storage virtualization is to overcome vendor interoperability issues. Storage array manufacturers may comply with the appropriate SCSI and Fibre Channel standards for basic connectivity to their products. Each, however, may also implement proprietary value-added utilities and features to differentiate their offerings in the market and these, in turn, may pose interoperability problems for customers with heterogeneous storage environments. By virtualizing vendor-specific storage into its vanilla flavor, storage virtualization products may be used to provide data replication across vendor lines. In addition, it may become possible to replicate data from higher-end storage arrays with much cheaper disk assets such as just a bunch of disks (JBODs), thus addressing both interoperability and economic issues.
The concept of a system level storage virtualization strategy includes a utility service that may be accessed reliably and transparently by users. Reliability implies that storage data is highly accessible, protected, and at expected performance of delivery. Transparency implies that the complexity of storage systems has been successfully masked from view and that tedious administrative tasks have been automated on the back end. The abstraction layer of storage virtualization may bear the burden of preserving the performance and data integrity requirements of physical storage while reducing the intricate associations between physical systems to a simple utility outlet into which applications can be plugged.
Various disks that may include cylinders, heads, and sectors may be virtualized into logical block addresses, logical blocks from disparate storage systems may be pooled into a common asset, tape drives and tape systems may be virtualized into a single tape entity, or subdivided into multiple virtual entities, entire file systems may be virtualized into shared file systems, and files or records may be virtualized on different volumes. Virtualization may occur on the host, in storage arrays, or in the network via intelligent fabric switches or SAN-attached appliances. The virtualization may occur via in-band or out-of-band separation of control and data paths. Treating multiple physical disks or arrays as a single logical entity may segregate the user of storage capacity from the physical characteristics of disk assets, including physical location and unique requirements of the physical devices. Storage capacity for individual servers, however, may still be configured, assigned, and monitored.
The abstraction layer that masks physical from logical storage may reside on host systems such as servers, within the storage network in the form of a virtualization appliance, as an integral option within the SAN interconnect in the form of intelligent SAN switches, or on storage array or tape subsystem targets. These alternatives may be referred to as host-based, network-based, or array-based virtualization. The in-band method may place the virtualization engine in the data path, so that both block data and the control information that governs its virtual appearance may transit the same link. The out-of-band method may provide separate paths for data and control, presenting an image of virtual storage to the host by one link and allowing the host to directly retrieve data blocks from physical storage on another.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.